Synthesis of CNT-reinforced AZ31 magnesium alloy composites with uniformly distributed CNTs

An effective two-step dispersion process for producing carbon nanotube (CNT)-reinforced magnesium alloy (CNT/AZ31) composites was developed, and the microstructure and the mechanical properties of the composite were investigated. The process includes the preparation of a CNT/Mg precursor with uniformly dispersed CNTs and the synthesis of CNT/AZ31 composites by subsequent melting and hot extrusion. An analysis showed that the CNTs uniformly disperse in the molten AZ31 without agglomeration because of the use of the CNT/Mg precursor. The structure of the CNTs was not destroyed, and good interfacial bonding existed between the CNTs and the AZ31 matrix. The tensile yield strength of the CNT/AZ31 composite was 22.7% greater than that of the monolithic AZ31 alloy without an obvious decrease in elongation and the compressive yield strength increased by 53 % with the addition of 0.05 vol. % CNTs. The reasons for the increase in strength are the decrease in grain size of the matrix due to the heterogeneous nucleation effect of the CNTs and the good interfacial bonding between the CNTs and the matrix. In addition, the compressive strength of the CNT/AZ31 composites was sensitive to the grain size, which implies that the addition of CNTs affects the compression behaviour of the CNT/AZ31 composites.